Method for data traffic policing, a data traffic policer realizing such a method and a telecommunication network including such a data traffic policer

ABSTRACT

The present invention concerns a method for use in a telecommunication network by a data traffic policer (POL) for data traffic policing on a data communication link (L). The data traffic includes data cells that are grouped into frames (F 1 , F 2 , F 3 , . . . ). The method comprises the step of for each data cell of a frame (F 2 ), upon reception of the data cell, checking a conformance of the data cell and providing thereby a conformance result of the data cell being any one of conforming and non-conforming (F/T). The method further includes the steps of storing the data cell into a buffer (BUFF) and treating the frame as conforming in the event when for each data cell of the frame that is stored in the buffer (BUFF) the conformance result is conforming (F); and in the event when the frame is treated as conforming (F) and upon reception of a predefined data cell of the frame (F 2 ), starting transmission of a predefined number of data cells of the frame (F 2 ) by the traffic policer (POL).

BACKGROUND OF THE INVENTION

The present invention relates to a method for use in a telecommunicationnetwork by a data traffic policer, to a data traffic policer realizingsuch a method and to a telecommunication network including such a datatraffic policer.

Such a method to police data traffic realized by such a data trafficpolicer is already known in the art e.g. from two contributions to the‘ATM Forum Technical Committee’ and distributed to the ‘ATMF TrafficManagement Working Group’. The first one, written by O. Bonaventure, P.Frêne and E. Desmet, with the aim to stimulate the formalization of thecurrent textual conformance definition for the Guaranteed Frame Rateservice category, was made available to the public on Feb. 8-13, 1998 atAnaheim, Calif., reference 98-0059. The second one, written by O.Bonaventure and E. Desmet, with the aim to discuss the possible optionsfor a formal Guaranteed Frame Rate GFR conformance definition andpropose of choice, was made available to the public on Apr. 20-24, 1998at Berlin, Germany, reference 98-0281. These documents will be referredto by the reference numbers 98-0059 and 98-0281, respectively, in thisapplication.

Both documents are describing conformance definitions for the GuaranteedFrame Rate service GFR category. Data traffic policing on a datacommunication link is performed for data traffic including data cellsbeing grouped into frames. Upon reception of a data cell at such a datatraffic policer, the data cell is checked upon its conformance by adecision means. The decision means provides a conformance result that iseither conforming or non-conforming.

According to the 98-0281 document, each arriving data cell of a frame isverified upon its conformance by a conformance test e.g. a Peak CellRate test PCR, or Cell Delay Variation Tolerance test CDVT according toa Guaranteed Frame Rate GFR contract of a user. In the event that thehead of a frame is conforming i.e. each data cell of the head of theframe is conforming, and a non-conforming data cell arrives, thefollowing data cells of this frame i.e. the tail of the frame, exceptthe last cell, is also declared as non-conforming.

It has to be explained that according to the management strategy of theoperator a non-conforming cell is discarded or is marked asnon-conforming. Marking a non-conforming data cell is called tagging.Furthermore, the tagged data cells and tagged frames are counted by theoperator.

When the non-conforming cells are e.g. discarded, the conforming cellsof the same frame which are already distributed into the network,becomes part of an incomplete frame which makes these conforming datacells also non-conforming. When the non-conforming data cells are e.g.marked, according to predefined statistic rules of the operator it isdecided that at a predefined amount of non-conforming traffic, aconnection is interrupted which makes again that conforming frames orconforming cells which are already distributed into the network arebecoming non-conforming.

In this way, the conforming head of a frame that is distributed in thenetwork becomes an incomplete frame and this incomplete frame utilizesnetwork resources before being discarded at its destination. Thisincomplete frame provides extra traffic to the network.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for datatraffic policing of the above known type but which provides an improveduse of the network resources i.e. a lower percentage of non-conformingdata cells being distributed in the network.

Indeed, the basic idea of the invention is based on the insight that bydirectly transmitting a conforming data cell, after its conformancecheck, into the network it is possible that it becomes later on anon-conforming data cell due to non-conformance of other cells insidethe frame which cause the entire frame to be non-conforming.

However, according to the present invention the data cells are bufferedinto a buffer means after its conformance check while a status meanskeeps track of a conformance status of the frame. The conformance statusof the frame is conforming as long that for each data cell of the framethat is stored in the buffer means the conformance result is conforming.A smaller risk is taken when, as long that the conformance status of theframe is conforming, only a predefined number of data cells of the frameis transmitted by a transmitting means upon reception of a predefineddata cell of the frame. This will become more clear with the example ofthe following paragraph.

Presume a situation wherein data cells of a frame are received, checkedupon its conformance and buffered by such a traffic policer. Allbuffered data cells have a conformance result that is conforming. Thismeans that the frame is still treated as conforming. Upon arrival of apredefined data cell e.g. a data cell in the middle of the frame, thedata traffic policer starts transmission of a predefined number of datacells e.g. a quarter of the total number of data cell of the frame,hereafter called first packet data cells. While this first packet datacells are transmitted into the network, the data traffic policercontinues its work i.e. reception of the following data cells of theframe, checking its conformance and storing them into the buffer.Presume that for the nearly last data cell of the frame its conformanceresult is non-conforming. This means that according to the knownconformance rules also the data cells received after this non-conformingdata cell are declared non-conforming. As described above, all theprevious data cells to this non-conforming data cell will become part ofan incomplete frame and are thereby also non-conforming. However, onlythe first packet data cells were transmitted into the network since theother data cells are still present in the buffer. Compared to the priorart situation i.e. without a buffer, the data traffic policer of thepresent invention provides an improved use of the network resources i.e.a lower percentage of non-conforming data cells are distributed in thenetwork.

An implementation of the present invention is that in the event when theframe is still treated as conforming and upon reception of thepredefined data cell of the frame which is determined by the last datacell of the frame, the frame is also declared by the status means asconforming when this last data cell has also a conformance result whichis conforming. The transmitting means starts transmission of apredefined number of data cells that is determined by the total numberof data cells of the frame. This means that a frame is declared to beconforming when all the data cells of a frame are conforming and onlywhen the frame is declared to be conforming all its data cells aretransmitted into the network.

Another characteristic feature of the present invention is that theconformance of the data cells is checked according to cell basedconformance rules or according to frame based conformance rules. Indeed,as it is described in the 98-0281 document, different options arepossible for e.g. a Guaranteed Frame Rate GFR conformance definition.These options are taking into account cell related features such as theCell Loss Priority bit, the Peak cell Rate and the Cell Delay VariationTolerance, and also frame related features such as the Maximum Framesize. Furthermore, more than one conformance test can be executed inorder to complete the conformance check according to the presentinvention, whereby a predefined structure is brought into the sequenceof the different conformance tests.

Finally, it has to be explained that a telecommunication network thatincludes a data traffic policer according to the present invention cansupport different kinds of Quality Of Service Categories whereby theconformance is checked according to the conformance definitions of thesupported service category. Such a supported service category is e.g.the unspecified Bit Rate service category or the Guaranteed Frame Rateservice category.

It should be noticed that the term “including”, used in the claims,should not be interpreted as being limitative to the means listedthereafter. Thus, the scope of the expression “a device including meansA and B” should not be limited to devices consisting only of componentsA and B. It means that with respect to the present invention, the onlyrelevant components of the device are A and B.

Similarly, it is to be noted that the term “coupled”, also used in theclaims, should not be interpreted as being limitative to directconnections only. Thus, the scope of the expression “a device A coupledto a device B” should not be limited to devices or systems wherein anoutput of device A is directly connected to an input of device B. Itmeans that there exists a path between an output of A and in input of Bwhich may be a path including other devices or means.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the invention will becomemore apparent and the invention itself will be best understood byreferring to the following description of an embodiment taken inconjunction with the accompanying FIG. 1 which illustrates a blockdiagram of a data traffic policer according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the working of the data traffic policer POL will beexplained by means of a functional description of the blocks showntherein. Based on this description, implementation of the functionalblocks will be obvious to a person skilled in the art and will thereforenot be described in detail. In addition, the principle working of thedata traffic policer regarding the invention will be described infurther detail.

According to FIG. 1, the data traffic policer is coupled on a datacommunication link L of a telecommunication network. The datacommunication link L is coupled to an input IN and to an output OUT ofthe data traffic policer. The data traffic on the data communicationlink L includes data cells that are grouped into frames. FIG. 1 showssome data cells on the communication link L.

The traffic policer POL includes three functional blocks: a decisionmeans DEC, a status means STAT and a buffer means BUFF. The decisionmeans is coupled to the input IN of the data traffic policer POL and isimplemented by a first processor. The status means is coupled to thedecision means and is implemented by a second processor. The buffermeans BUFF is coupled to the decision means DEC and to the status meansSTAT. The buffer BUFF is furthermore coupled to the output OUT of thedata traffic policer POL.

Upon reception of a data cell of a frame by the data traffic policer,the decision means DEC checks the conformance of the data cell. Thisaction is executed according to different steps. For this preferredembodiment each data cell is checked upon its conformance according tothe overall Guaranteed Frame Rate GFR conformance definition asdescribed according to the first main test of the cited prior artdocument with reference 98-0059. As it is described in this document atparagraph 3, the overall GFR conformance definition is composed of twomain tests that operate in sequence. The first test verifies theconformance of the cell flow to the maximum frame size MFS, the peakcell rate PCR, the cell delay variation tolerance CDVT and the cell losspriority bit CLP of the traffic contract. These four formalizedconformance definitions are described in paragraph 4 of the referreddocument ATM-Forum/98-0059:

4.1 MFS conformance definition;

4.2 PCR conformance definition;

4.3 Frame delineation;

4.4 CLP conformance definition; that is hereby incorporated byreference. The information required to implement the four tests of thedecision means DEC is obtainable from this document. By executing thesefour tests, the decision means DEC provides a conformance result for thedata cell that equals conforming or non-conforming data cell.

It has to be remarked that one of the steps during the conformance checkis to detect the position of the received data cell in its frame: firstcell, middle cell or last cell of a frame. This information will also beused later on by the buffer means BUFF and the status means STAT.

The conformance result is included in a first control signal CTRL1 andis provided by the decision means DEC to the status means STAT. The datacell itself is provided by the decision means DEC to the buffer meansBUFF.

The buffer BUFF stores the data cell according to the frame whereto thedata cells belongs. This means that the buffer BUFF must known to whatframe the data cell belongs. In order to realize this, the buffer BUFFis coupled via an extra control connection to the decision means. Viathis control connection a second control signal CTRL2 is provided to thebuffer means BUFF. This second control signal CTRL2 includes the frameidentity e.g. F2 of the frame whereto the transmitted data cell belongs.With this information the buffer BUFF is enabled to manage the bufferingof data cells per frame.

It has to be remarked that the use of a second control signal CTRL2 inorder to forward the identification of a frame of a data cell is only apossible implementation of the present invention. Indeed, in e.g. an ATMnetwork the fields of Virtual Channel Identifier and Virtual PathIdentifier of the ATM data cells itself can be used as identification ofthe frame to which the data cell belongs whereby the second controlsignal CTRL2 is not needed anymore.

Furthermore the functional block of the buffer BUFF includes atransmitter to transmits the data cells of a particular frame to theoutput OUT of the data traffic policer POL upon reception of a thirdcontrol signal CTRL3 from the status means STAT. This transmitter of thebuffer BUFF is not shown in FIG. 1 in order not to overload FIG. 1. Thethird control signal CTRL3 will be further explained in a followingparagraph.

The status means STAT keeps track of the conformance result for eachdata cell of each frame. In stead of e.g. storing for each data cell ofeach frame its conformance result it is preferred for this embodiment towork with only one parameter for each frame. Indeed, a frame is treatedas conforming as long as for each data cell of the frame its conformanceresult is conforming. Once the conformance result for one data cell wasnot conforming the frame is not treated as being conforming anymore.This information is implemented with a non-conforming frame NCFparameter for each frame. Furthermore, together with the conformanceresult, also the position of the data cell in its frame and thereference of the frame, as described above, are included in the firstcontrol signal CTRL1 that is provided by the decision means DEC to thestatus means STAT. Upon reception of a first data cell of a frame, thisnon-conforming frame parameter is initialized to a value “false” F. Aslong that each conformance result of each received data cell of aparticular frame is conforming this value “false” F will be kept. Thismeans that each time that a data cell is checked upon its conformanceand the conformance result is provided to the status means, the statusmeans interprets the conformance result. The non-conforming frame NCFparameter of the associated frame is remained to the value “false” Fwhen the conformance result is conforming and is changed to the value“true” T when the conformance result is non conforming. Referring to thestatus means STAT of FIG. 1, the status of the non conforming frameparameter is shown with a table: the first column of the table gives areference to the different frames e.g. F1, F2, F3, . . . ; the secondcolumn of the table provides the value of the non conforming frameparameter NCF of the associated frame e.g. for frame F1 the NCF value isfalse which is shown with F and for frame F3 the NCF value is true whichis shown with T. The table further includes a third column that will beexplained in a further paragraph.

It has to be explained that for this particular embodiment it ispreferred to start transmission of a total frame, in the event that theNCF parameter is still false F, upon reception of the last data cell ofa frame. This means that in the event when the last data cell of a frameis checked by the decision means DEC upon its conformance, a firstcontrol signal CTRL1 is provided to the status means STAT. The firstcontrol signal CTRL1 includes the end of frame information and theconformance result of this last data cell. When this conformance resultis conforming and the non-conforming frame parameter of the relatedframe is still false F. the status means STAT will not change thisvalue. The fact that a last data cell of a frame is received is shown inthe third column of the table. Upon reception of a first data cell of aframe, the value of a parameter “end of frame” EOF associated to thereferred frame e.g. F1 is initialized to a value “No” N. Now, uponreception of the end of frame indication, the value of the parameterassociated to the referred frame e.g. is changed to the value “Yes” Y.Once the two parameters of a particular frame i.e. non-conforming frameNCF and end of frame EOF have the value F and Y, respectively, thestatus means STAT declares the frame as conforming. When a frame isdeclared as conforming a third control signal CTRL3 is generated andprovided to the buffer BUFF. The third control signal CTRL3 includes thereference to the frame being declared as conforming whereby the bufferBUFF is permitted to start transmission of this referred frame.

It has to be remarked that although this preferred embodiment isdescribed with the inclusion of an “End Of Frame” indication in thefirst control signal CTRL1, the invention is not restricted to anapplication with such an inclusion. Indeed, the described embodiment canbe adapted with small modification, evident to a person skilled in theart to explain the use of a data traffic policer with no explicitinclusion of the “End Of Frame” in such a first control signal CTRL1e.g. in an ATM network the End Of Frame is part of the ATM cell i.e. AUUbit whereby the “End Of Frame” indication is extracted from the datacell itself in order to update the related parameter.

Furthermore the status means STAT also generates a fourth control signalCTRL4 in the event when the non-conforming parameter NCF for aparticular frame e.g. F3 became true T i.e. the status means STATreceived a conformance result of a data cell of this frame F3 that isnon-conforming. At this point it is known to the data traffic policer,that this frame will never be conforming. As it is described in aprevious paragraph the data traffic policer marks or discards thisnon-conforming data cell, according to the operator its strategy.Furthermore the next incoming data cells of this frame will also bemarked or discarded. Finally, the data traffic policer POL counts thenon-conforming data cells.

An advantage of the present invention becomes clear now. Indeed, thedata traffic policer is also able to mark or to discard the alreadybuffered data cells of a frame that became non-conforming. Indeed, thesedata cells are buffered in the buffer BUFF and are not yet distributedinto the network. This makes that in the event when a non conformingdata cell is received at the data traffic policer its frame is declaredto be non-conforming. At this moment, not part of its data cells, butall its data cells will be marked or discarded: the already buffereddata cells i.e. head of a frame is immediately marked or discarded andthe data cells of the tail of the frame will be marked or discarded uponarrival at the data traffic policer. Since, according to this situationand implementation, it is sure that the first data cell of a frame isalways marked or discarded, whereby the data traffic policer ispermitted to mark or to discard also the last cell of that frame.Indeed, no last data cell of a frame must be retained for the first datacell of that frame that, however, already was distributed into thenetwork.

It is clear that the related action i.e. discarding or marking of aframe is initiated by the fourth control signal CTRL4 that is generatedby the status means STAT. However, the detailed description of thisrelated action goes beyond the scope of this invention and will not bedescribed in this application in further detail.

In order to explain the functional working of the present invention apreferred situation will be described in details by means of an example.

Referring to FIG. 1, presume a situation whereby the buffer BUFF isfilled with data cells according to the its associated frame. In thisway for

Frame F1 four data cells are buffered; and for

Frame F2 ten data cells are buffered; and for

Frame F3 six data cells are buffered.

On the other hand the table of the status means STAT includes thefollowing information values for the parameters:

Frame NCF EOF F1 F N F2 F N F3 T N . . .

According to this table information e.g. frame F2 is still treated asconforming since its non-conforming frame parameter is “false”. Thismeans that for each data cell of frame F2 that is stored in the bufferBUFF the conformance result was conforming. Furthermore, according tothe table information, the last data cell of frame F2 is not yetreceived.

Presume a situation wherein the last data cell of frame F2 just enteredthe decision means DEC. The decision means DEC starts checking theconformance status of this data cell. Presume that the outcome accordingto the flow diagrams of the conformance tests of the referred paragraphsof the referred document is that this data cell has a conformance resultthat is conforming.

This conformance result is included together with the reference to theframe F2 and the “end of frame” information in the first control signalCTRL1. The first control signal CTRL1 is provided by the decision meansDEC to the status means STAT. The table of the status means STAT isupdated i.e. the value for the non-conforming parameter of frame F2remains “false” F and the value for the end-off-frame parameter ischanged to “Yes” Y:

Frame NCF EOF F1 F N F2 F Y F3 T N . . .

Furthermore the decision means DEC provides the data cell itself to thebuffer means BUFF. The reference to the frame F2 is included in thesecond control signal CTRL2 and is also provided to the buffer meansBUFF, The buffer means BUFF stores the data cell together with the otherdata cells of the frame F2.

Since the two parameters associated to frame F2 have the value F and Y,the status means STAT declares the frame F2 as conforming. Indeed, theconformance result of the last data cell of the frame F2 is alsoconforming. The status means STAT generates a third control signalCTRL3. The third control signal CTRL3 includes the frame F2. Uponreception by the buffer BUFF of the third control signal CTRL3 thebuffer is allowed to start transmission of the frame referred to in thethird control signal CTRL3 i.e. F2. The buffer BUFF starts transmissionof this total frame F2 that is declared as conforming.

It has to be remarked that although it is preferred for this particularembodiment to start transmission of the frame upon receiving of the lastdata cell of the frame, the data cell starting transmission of the framehas not to be the End Of Frame, but can be any predetermined cell of theframe.

A further remark is that although according to this preferred embodimentthe data traffic policer is coupled to a communication link, it isevident to a person skilled in the art that a other devices such as ashaper or a complete ATM switch could be coupled instead of.

Finally, it has to be remarked that although this preferred embodimentis described in an Guaranteed Frame Rate environment, the invention isnot restricted to an application in an Guaranteed Frame Rateenvironment. Indeed, the described embodiment can be adapted with smallmodifications, evident to a person skilled in the art to explain the useof the data traffic policer in another kind of Quality Of Servicecategory, such as e.g. the unspecified Bit Rate Service category.

While the principles of the invention have been described above inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationon the scope of the invention, as defined in the appended claims.

What is claimed is:
 1. A method for data traffic policing in atelecommunication network by a data traffic policer on a datacommunication link, said data traffic including data cells which aregrouped into frames, said method comprising: for each data cell of aframe, upon reception of said data cell, checking a conformance of saiddata cell according to predefined conformance rules and providing aconformance result of said data cell being any one of conforming andnon-conforming; storing said data cell into a frame buffer andindicating said frame as conforming when, for each data cell of saidframe being stored in said frame buffer, said conformance result isconforming; and in the event that both said frame is conforming and apredefined data cell of said frame is received, starting transmission ofa predefined number of data cells of said frame by said traffic policer.2. The method according to claim 1, said method further comprises that,in the event when said frame is indicated as conforming and saidpredefined data cell which is a last data cell of said frame isreceived, declaring said frame as conforming when said conformanceresult of said last data cell is also conforming, and startingtransmission of said predefined number of data cells which is a totalnumber of data cells of said frame.
 3. The method according to claim 1,wherein said predefined conformance rules are any one of cell basedconformance rules and frame based conformance rules.
 4. A data trafficpolicer to be used in a telecommunication network for data trafficpolicing on a data communication link, said data traffic includes datacells which are grouped into frames, said data traffic policercomprising: a decision means coupled to an input of said data trafficpolicer to check for each incoming data cell of a frame for conformanceaccording to predefined conformance rules and to provide thereby aconformance result of said data cell which is any one of conforming andnon-conforming; a frame buffer means coupled to said decision means tostore said checked data cell; and a status means coupled to saiddecision means to store a conformance status of said frame whereby saidconformance status of said frame is conforming in the event each datacell of said frame being stored in said frame buffer means isconforming; and a transmitting means to start transmission of apredefined number of data cells of said frame upon both the reception ofa predefined data cell of said frame by said data traffic policer andsaid conforming status of said frame is still conforming.
 5. The datatraffic policer according to claim 4, wherein said status means isfurther adapted to declare said frame as conforming upon reception ofsaid predefined data cell which is a last data cell of said frame and inthe event when said conforming status of said frame is still conformingand when said conformance result of said last data cell is alsoconforming, and said transmitting means is adapted to start transmissionof said predefined number of data cells which is a total number of datacells of said frame and.
 6. A telecommunication network, wherein saidtelecommunication network includes a data traffic policer according toclaim
 4. 7. The telecommunications network according to claim 6, whereinsaid telecommunication network supports a guaranteed frame rate servicecategory and that said conformance is checked according to conformancedefinitions of said guaranteed frame rate service category.
 8. Themethod according to claim 1, said method further comprising marking alldata cells stored in said frame buffer as non-conforming when saidconformance result of one data cell is non-conforming.
 9. The methodaccording to claim 1, said method further comprising treating said frameas non-conforming when said conformance result of at least one data cellstored in said frame buffer is non-conforming.
 10. The data trafficpolicer according to claim 4, wherein all data cells stored in saidframe buffer means for said frame are marked as non-conforming when saidconformance result of one data cell is non-conforming.
 11. The datatraffic policer according to claim 4, wherein said status meansindicates said frame as non-conforming when said conformance result ofat least one data cell stored in said frame buffer means for said frameis non-conforming.
 12. A data traffic policer to be used in atelecommunication network for data traffic policing on a datacommunication link, said data traffic includes data cells which aregrouped into frames, said data traffic policer comprising: a decisiondevice coupled to an input of said data traffic policer to check foreach incoming data cell of a frame for conformance according topredefined conformance rules and to provide thereby a conformance resultof said data cell which is any one of conforming and non-conforming; aframe buffer coupled to said decision device to store said checked datacell; and a status device coupled to said decision device to store aconformance status of said frame whereby said conformance status of saidframe is conforming in the event when for each data cell of said framebeing stored in said frame buffer said conformance result is conforming;and a transmitter to start transmission of a predefined number of datacells of said frame upon both the reception of a predefined data cell ofsaid frame by said data traffic policer and said conforming status ofsaid frame is still conforming.
 13. The data traffic policer accordingto claim 12, wherein said status device is further adapted to declaresaid frame as conforming upon reception of said predefined data cellwhich is a last data cell of said frame and in the event when saidconforming status of said frame is still conforming and when saidconformance result of said last data cell is also conforming, and saidtransmitter is adapted to start transmission of said predefined numberof data cells which is a total number of data cells of said frame. 14.The data traffic policer according to claim 12, wherein all data cellsstored in said frame buffer for said frame are marked as non-conformingwhen said conformance result of one data cell is non-conforming.
 15. Thedata traffic policer according to claim 12, wherein said status deviceindicates said frame as non-conforming when said conformance result ofat least one data cell stored in said frame buffer for said frame isnon-conforming.